Tobacco substitute or synthetic smoking materials have been known for some time. Such materials, which may be included in smoking articles as the sole smokeable material or in admixture with natural tobacco, may be employed for economic reasons, or to affect the composition of the smoke resulting from a smokeable article.
Numerous tobacco substitutes are known; typical tobacco substitutes are described in, e.g., U.S. Pat. Nos. 2,809,904; 3,410,276; 3,461,879; 3,477,865; and 3,732,392. Generally, such tobacco substitutes comprise a binder, a fibrous filler, such as asbestos or kraft pulp, to impart strength to the tobacco substitute sheet and a combustion control or burning rate modifying agent. In some instances, substitutes may also require an ash control agent.
Another tobacco substitute is disclosed in copending U.S. application Ser. No. 527,175, filed on Nov. 25, 1974 by David G. Strubel and Robert R. Johnson, and entitled "Tabacco Substitute Containing Boric Oxide, Boric Oxyacids, and Ammonium, Alkali Metal, or Alkaline Earth Metal Salts of Boron Oxyacids."
Tobacco substitutes desirably have a number of properties which are analogous to those of natural tobacco. For example, tobacco substitutes should have burning characteristics which are compatible with natural tobacco. However, some otherwise suitable tobacco substitute compositions burn too rapidly or at too high a temperature to be suitable for use as smokeable items. In order to overcome this disadvantage, constituents such as hydrated alumina have been incorporated into the reconstituted tobacco as combustion control or burning rate control agents.
Another problem with many tobacco substitute compositions is that they tend to "bloom" upon combustion. Blooming occurs when the ash expands, becomes incoherent and disintegrates. Often in cigarettes containing blends of tobacco and tobacco substitutes, rather than forming a natural-appearing coherent ash, the filament or ribbon-like ashes of the tobacco and tobacco substitute particles separate and peel out from the center of the ash causing blooming. The expanded ash has a very unattractive appearance and is weakened to the degree that large hot particles flake off. Another characteristic of such an ash is its tendency to fall off prematurely with little or no agitation of the cigarette.
Various materials are known to affect ashing properties, and in some instances, fibrous materials have served both to support the ash after combustion and to impart strength to the substitute sheet. Fibrous materials used to support tobacco substitute ash include asbestos or cellulosic materials, such as cellulose gauze treated with a flameproofing agent.
The present invention pertains to tobacco substitutes produced in the form of coherent sheets which can be subsequently shredded into a form suitable for use in smokeable products. The product of the present invention, in admixture with tobacco, has a burn rate which is suitable for use in a smokeable product. In addition, the compositions of the present invention, upon combustion, form a stable, normal-appearing, non-blooming ash. Furthermore, the tobacco substitutes of the present invention do not impart undesirable taste to smokeable products, and may be economically produced.